Broadband communication systems are known in the art. The main types include video oriented communication systems and data oriented communication systems. Video oriented communication systems were originally designed for television broadcast transmissions and today include modifications, which enable narrow-cast transmissions as well as data communications there through. Data oriented communication systems are used for a plurality of data and multimedia applications. Conventionally, downstream channels (from the cable service operator to the end user) are used to carry either only IP packets (using DOCSIS for example) or only native MPEG programs over MPEG transport. This requires the cable operator to perform fixed allocation of downstream resources for different services, which limits the resource usage efficiency, especially for the downstream bandwidth.
Cable Modem Termination Systems (CMTS) are known in the art. Such systems are installed in a cable head-end and are connected to a plurality (conventionally thousands) of Cable Modems (CM) via a Hybrid Fiber/Coaxial (HFC) Network. A conventional single CMTS board transmits downstream information on a single channel and receives upstream information from one or more (usually not more than 8) upstream channels. Upstream channels which are connected to a single CMTS board, can be received from many nodes (usually for areas which are characterized by a small number of cable modem users) or from a single node (usually for areas which are characterized by a large number of cable modem users).
The operation of a conventional CMTS is generally predefined, where the cable modem users are configured to utilize a specific CMTS downstream channel. Each CMTS downstream channel has specific associated upstream channels. The CMTS board uses its associated downstream channel, to provide upstream channels and time slot information to the CMs on which they can transmit information back to the head-end, at any given time.
An article, “Multimedia Traffic Engineering for HFC Networks” by John T. Chapman from Cisco Systems (Nov. 29, 1999), discusses possible CMTS architectures contingent on penetration of CMs and broadband services.
Using prior art systems, DOCSIS upstream channels are rigidly coupled to their associated downstream channel. In high penetration areas serving high bandwidth applications, there is a need to provide several downstream channels per each given node. Accordingly, the entire group of cable modem subscribers in that node has to be divided into smaller groups, where each group is assigned and served by a separate downstream channel, and some upstream channels that are associated therewith. It will be appreciated by those skilled in the art that this architecture utilizes upstream bandwidth inefficiently, since upstream resources are fixed allocated to each group rather than dynamically allocated between the groups, which are associated with the same node. In addition, there is a major reliability/redundancy hazard in a case where only one upstream channel is allocated to each DOCSIS MAC domain (i.e. for each downstream channel).
Digital video and other media are typically transmitted in a compressed form, encapsulated in MPEG transport packets, which include information associating them to a specific stream. It is noted that MPEG transport packets do not include neither source address information nor destination address information and hence can not be switched, using networking methods and systems, which are known in the art.
U.S. Pat. No. 5,719,862 to Lee, et al., and entitled “Packet-Based Dynamic De-Skewing for Network Switch with Local or Central Clock”, is directed to a network switch with packet-based de-skewing. A switch core switches between a plurality of source media-access controllers (MAC's) and a plurality of destination MAC's. Each source MAC is provided with a framer, and each destination MAC is provided with a de-skew circuit. A clock source provides input to each framer and each de-skew circuit. Each link is provided with a single serial data line through the switch core. The framer receives a serial data packet from the source MAC, and adds a start flag sequence (header) to the packet. As communication links are broken and new links are established, the new links introduce a different amount of skew. The de-skew circuit measures the clock skew of the packet received through the new link, by comparing the phases of the received start flag sequence, and a known start flag sequence.
U.S. Pat. No. 5,742,761 to Olnowich, et al., entitled “Apparatus for Adapting Message Protocols for a Switch Network and a Bus”, is directed to a system for inter-linking a plurality of computers connected to a switch network. Each computer is connected to a Micro-Channel (MC) converter unit via a MC bus, and each MC converter is connected to the input and output port of the switch network. Each of the computer resources such as processor, memory, and I/O units is connected to a slot on the MC bus. The MC converter converts the address of a resource on a remote computer, as requested by a client, to a means for locating the exact MC island. The switch network establishes the link between the client and the remote computer. The client transfers data to the MC converter of the remote computer, and this MC converter transfers the data to the designated slot on the MC bus of the remote computer. Then, the designated resource of the remote computer receives the data.
U.S. Pat. No. 5,781,726 to Preira, entitled “Management of Polling Traffic in Connection Oriented Sessions”, is directed to a system for connecting an end station in a first local area network (LAN), to an end station in a second (LAN). The first LAN is connected to a central node (CN), and the second LAN is connected to a leaf node (LN). The CN and the LN are interconnected by an intermediate session link. An end station in the first LAN establishes connection with an end station in the second LAN, by a first link session, the intermediate session link, and a second link session. The first link session connects the end station in the first LAN to the CN, and the second link session connects the LN to an end station in the second LAN.
U.S. Pat. No. 5,748,626 to Esaki, et al., entitled “ATM Communication System With High Speed Connection-Less Service Function”, is directed to a system for transferring ATM cells between a plurality of ATM networks, equipped with connection-less service function. The ATM networks are interconnected by an inter-networking unit (IWU). The IWU unit includes an ATM switch of N inputs and M outputs, a call processing unit and an IWU management unit connected to the ATM switch. The IWU unit further includes N input processing units for entering inputs from N ATM networks, and M output processing units for outputting outputs to M ATM networks. The call processing unit sets up, cuts off, changes, and manages the ATM connection over the IWU. The IWU management unit manages and controls the IWU.
Each of the input processing units analyzes the header value of the entering ATM cell, converts the header value if necessary, and attaches a routing tag for appropriate routing of the ATM cell. Each of the output processing units removes the routing tag from the cell, and converts the header value if necessary. The ATM switch switches the outputs of the N input processing units, the call processing unit, and the IWU management unit, into the inputs of the M output processing units, the call processing unit, and the IWU management unit.